How far is too far, in the effort to teach the public about global warming?

A U.K. group called Plane Stupid is drawing fire for a new ad they’re airing, which depictes polar bears chucked from planes and falling to their death. It’s meant to illustrate the point that every plane flight emits about 880 pounds of carbon-dioxide–about the weight of a polar bear.

He goes on to make a very interesting point: Shock ads tend to work in cases like safe-sex, when it’s a matter of making smarter personal decisions. You see a memorable ad, and you think twice before unprotected sex.

Shock ads like this one, meanwhile, pose a danger in themselves: If the theme of combating climate change begins verging on propaganda, then you risk having the public see it as one of political disposition, rather than something overwhelmingly supported by science. But then again, how else do you reach a public increasingly inured to advertising and largely ignorantof science?